linux-kernel - Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks

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Date:	Mon, 14 Dec 2015 09:36:25 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"Luck, Tony" <tony.luck@...el.com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover
 from machine checks


* Andy Lutomirski <luto@...capital.net> wrote:

> I still think it would be better if you get rid of BIT(63) and use a
> pair of landing pads, though.  They could be as simple as:
> 
> .Lpage_fault_goes_here:
>     xorq %rax, %rax
>     jmp .Lbad
> 
> .Lmce_goes_here:
>     /* set high bit of rax or whatever */
>     /* fall through */
> 
> .Lbad:
>     /* deal with it */
> 
> That way the magic is isolated to the function that needs the magic.

Seconded - this is the usual pattern we use in all assembly functions.

Thanks,

	Ingo
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